Field of the Invention
The present invention relates to electronics and, more specifically but not exclusively, to multi-band combiners for wireless cellular communications.
Description of the Related Art
This section introduces aspects that may help facilitate a better understanding of the invention. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art.
In wireless cellular communications, each cell tower may be used to support multiple technologies (e.g., GSM, CDMA, WCDMA, LTE, etc.) deployed in different frequency bands (e.g., 800 MHz, 900 MHz, 1900 MHz, etc.). In such situations, a multi-band combiner may be used to combine multiple transmit (i.e., downlink) signals in multiple different downlink frequency bands for simultaneous transmission from a single antenna. Such di/tri/quad/penta band-plexers employed at the base of the cell tower reduce the number of RF feeder runs between the radios at the base of the tower and the antenna(s) at the top of the tower. Using such multi-band combiners significantly reduces the capital expenditure by combining different bands with each multi-band combiner and running the resulting, single, combined signal to the antenna.
Combining different bands at different frequencies into a single multi-band signal generates passive inter-modulation (PIM) products at various frequencies. These PIM products can constitute interfering noise if one or more of them (i) fall within one or more of the uplink frequency bands and (ii) are strong enough to desensitize the corresponding radio receiver(s).